This invention relates generally to electromagnetic circuit breakers of the type having a housing made in two half sections, each of which is of molded plastic dielectric material. The half sections are held together by fasteners so as to support the circuit breaker mechanism and terminal components between these half sections.
Electromagnetic circuit breakers are designed to provide a load current and voltage through an electromagnetic coil that surrounds a delay tube in which a plunger or core is adapted to be drawn towards a pole piece at the end of the delay tube by reason of the magnetic flux created in a frame and armature. The frame is mounted between the circuit breaker half sections to support both the electromagnetic coil, on a bobbin or the like, and to also support a circuit breaker mechanism that is adapted to be tripped by the armature. The armature engages a sear to open the electrical contacts provided in an arc chamber also defined in the housing. The arc chamber is vented to release the gasses generated by the contacts on opening to avoid the buildup of excessive heat and pressure within the circuit breaker housing. U.S. Pat. No. 3,997,746 illustrates such an arc chamber and one object of the present invention is to provide for an improved arc chamber configuration with improved dielectric fortification between the terminal associated with the fixed contact in the bottom of the circuit breaker housing and an adjacent rivet provided to hold the housing half sections in assembled relationship.
In order to provide for remote and/or automatic tripping of the breaker a relay coil is provided in a separate electric control circuit. The circuit to be protected (the load circuit) is conventionally configured to achieve electromagnetic operation of the breaker in response to an overcurrent condition. The control circuit provides for selective tripping of the breaker. Thus, another object of the sent invention is to provide for an improved electromagnetic coil configuration, and more particularly for the bobbin that supports the coil, such that the breaker can be assembled with or without such a relay coil, and so that one design is possible for the frame, delay tube, pole piece and solenoid core or plunger. These components are provided in a single design circuit breaker assembly that may be fitted with a relay coil that allows the contacts to be tripped remotely.
Molded case electromagnetic split case circuit breakers must also accommodate a variety of stud or terminal configurations. For example, with a relay coil provided in the breaker as referred to above, additional or auxiliary terminals are required to provide the relay coil with the voltage necessary to pull the armature in and thereby to trip the breaker. Auxiliary terminals are conveniently provided in an optionally used terminal strip that may or not be provided in the molded case circuit breaker depending upon the design requirements of a particular installation. Alternatively, an auxiliary switch case is designed to fit an opening provided for this purpose in the bottom wall of the split case electromagnetic circuit breaker housing.